Silencer



March 24, 1942. c. c. Moss SILENQER Filed Aug. '28, 1939 INVENTOR heserC'. Nass BY I f%9flc4.

. A oRNEYs.

Patented Mar. 24, 1942 SILENCER Chester C. Moss, Jackson, Mich.,assigner to Walker Manufacturing Company of Wisconsin, a corporation ofWisconsin Application August 28, 1939, Serial No. 292,169

3 Claims.

The present invention relates to silencers, and particularly tosilencers especially designed for, but not restricted in theirapplication to, use as exhaust silencers for automobile engines.

The principal objects of the present invention are to provide a silencerof the above indicated type, and a method of making the same,characterized as embodying an improved arrangement for minimizing shellnoises, increasng the overall strength of the shell and otherwiseincreasing the efficiency of the silencer; to provide such aconstruction having a laminated shell embodying an outer shell memberand a cooperating inner shell member; to provide such an arrangementwherein the meeting edges of the inner shell are overlapped relative toeach other; and to generally improve the shell construction of exhaustsilencers.

With the above, as well as other objects in view, which appear in thefollowing description and in the appended claims, a preferred butillustrative embodiment of the invention is shown in the accompanyingdrawing, throughout the several views of which corresponding referencecharacters are used to designate corresponding parts, and in which:

Figure l is a view in longitudinal section of an exhaust silencerembodying the invention;

Fig. 2 is a View in vertical transverse section taken along the line 2-2of Fig. 1;

Fig. 3 is an enlarged fragmentary view, taken along the line 3 3 of Fig.1;

It will be appreciated that exhaust silencers conventionally comprise ashell-like structure having an inlet adapted for connection to theexhaust pipe of the associated engine, and having an outlet adapted forconnection to the usual tail pipe. The shell is conventionallyinteriorly provided with silencing structure, so constructed andarranged that as a consequence of the passage of the exhaust gasesthrough the shell from the inlet to the outlet thereof, theobjectionable sounds thereof are partially or entirely silenced.

By'virtue of the fact that the exhaust gases are delivered from theengine to the silencer as a succession of pressure impulses, it will beappreciated that the exhaust gases circulate through the shell atcontinuously and rapidly varying pressures. The circulation through theshell oi the exhaust gases under the just mentioned periodically varyingpressure conditions is generally regarded as accounting in large part atleast for producing objectionable sounds known as shell noises. Incertain instances, the shell noise is regarded as being produced.directly by the rapid changing of pressure within the shell, which rapidchanges cause expansion, and permit contraction, of the shell and incertain other instances, are regarded as being produced by thevimpinging against the shell of gaseous particles. Various expedientshave heretofore been proposed for the purpose of minimizing the shellnoises, but such expedients have not proven entirely satisfactory. Thearrangement described below has been found markedly effective insilencing shell noises and in otherwise improving the performance ofexhaust silencers.

It will be understood from a complete understanding of the inventionthat the improvements in the shell construction herein provided are, intheir broader aspects, applicable to a wide variety of silencerconstructions. By way of illustration, but not of limitation, however,the improvements of the present invention are herein illustrated inconnection with a silencer of the socalled three tube or retrovertedtype.

Referring to the drawing, the illustrated construction comprisesgenerally a shell, designated as a whole as I6, the respectivelyopposite ends whereof are closed by heads I4 and I6, and which isinteriorly provided with a silencing structure comprising the series ofparallel passages I8, 20, and 22, and the partitions 24, 26, and 28. Theinlet pipe 66, which is adapted for connection at its outer end to theusual engine exhaust pipe (not shown), extends through an openingprovided therefor in the head I4, and is rigidly connected thereto as bywelding at a plurality of points around the flange 32, which is formedin the head I4. The outlet 34, in turn, extends through a correspondinginwardly directed nipple 36 formed in the head I6, and iscorrespondingly rigidly secured thereto as by welding at a plurality ofpoints therearound. The inner end of the inlet 36 is telescoped over theend of the passage 20, which passage, in turn, passes through and issecured as by welding at the points 38', 4D, and 42, to the partitionmembers 24, 26, and 28. The inner end of the outlet 34 is secured to therear end of the exhaust passage I8, which passage in turn is secured tothe partitions 26 and 28 as by welding at the points 44 and 46. It willbe understood that the remaining passage 22 also extends between, andhas its ends welded to, the partitions 26 and 28.

The partitions 24 and 26 will be recognized as providing a transversepassage or cross-over 48, whereas the partition 28 and the header I6will be recognized as providing a corresponding crossover 56. Thepartition 24 and the header I4 in turn afford a silencing chamber 52,which is in acoustic communication with the cross-over 48 through anopening 54 formed in the partition 24.

It is preferred, as illustrated, to provide the tubes I8, 20, and 22, inthe portions thereof falling between the partitions 26 and 28, with aseries of louver openings 56 so as to afford acoustic communicationbetween the interiors of such tubes and the silencing chamber 58, whichlies between the partitions 26 and 28. In addition, in the illustratedconstruction, the tube I8 is provided with an additional shell member60, which, with the associated partitions 6I, 62, 63, and 64, define aplurality of small spit chambers surrounding the tube I8. Access fromthe interior of the tube I8 to the interior of the individual spitchambers is afforded through the louver openings such as 56 providedalong the body of the tube I8.

With the foregoing relation, it will be understood that the silencerprovides a primary exhaust passage for gases entering through the inlet30, which extends through the tube 28, the cross-over 50, the tube 22,the cross-over 48, and thence through the tube I8 to and through theoutlet 34. By virtue of the louver openings 56, the gases travelingthrough the just-mentioned path are enabled to circulate between each ofthe tubes I8, 28, and 22 and the silencing chamber 58. In addition,portions of the gases are enabled to pass into and out of the silencingchamber 52 through th'e openings 54. Portions of the gases passingthrough the tube I8 are also enabled to circulate into and out of thesmall spit chambers provided between the tube I8' and the inner shell60.

Referring now particularly to the construction of the shell itself, itwill be noted that the shell I8 is constituted by an outer cylindricalmember 10, the marginal edges whereof are rolled together in accordancewith conventional practice, to form a lock seam 12; and by an innershell member 14, disposed within the shell member 1D. The longitudinalmarginal edge portions 'I6 and 'I8 of the inner shell are in overlappedrelation to each other and are displaced from the seam 'I2 by an angleof approximately 180. The outer ends of the inner and outer shellmembers I4 and 'I0 are rolled with the marginal edge portions of theh'eads I4 and I6, so as to form the rolled seams 8U and 82, thusaffording a rigid and secure connection between the heads and the shellmembers.

In respect to the assembly of the above structure it is preferred toroll or otherwise bring the outer shell 'I0 from flat to cylindricalform, and form the lock seam 'I2 therein, in accordance withconventional practice. Thereafter, it is preferred to slide the innershell 'I4 into th'e outer shell and allow the inner shell, when properlypositioned therein, to expand slightly under the iniluence of its ownspring-like characteristics, so as to bring the outer surface of theinner shell into engagement with the corresponding inner surface of theouter shell. With the shell members thus preliminarily assembled, thesilencing structure, comprising the partition members and the conduitportions I8, 20, and 22, may be slid into place, after which the headsI4 and I6 may be applied to the ends of the shell members and secured inplace by means of the rolled seams 8|) and 82. To facilitate assembly,it is preferred to initially form the inner and outer shells ofsubstantially the same length,

and it will be understood that when the rolled seams and 82 are formed,some axial sliding occurs between the extrem'e end portions of the innerand outer shells, and that, in the completed seam, such extreme endssuch as 14a and 10a lie in slightly oifset relation to each other, as isclearly shown in Fig. 3.

The resultant construction has been found in practice, as previouslymentioned, to markedly improve the characteristics of exhaust silencers.Certain of the advantages resulting from the above described method andarrangement are as follows.

In respect to the reduction in shell noises, it will be appreciated thatthe above laminated construction produces the damping action which ischaracteristic of a laminated diaphragm or other element. That is tosay, the pressure impulses which are transmitted through the silencer,tend to cause vibratory movements of the inner and outer shell members,which vibratory movements produce the effect known as shell noise. Byvirtue of the fact that the inner and outer shells are in laminatedrelation to each other, however, or, stated otherwise, are in continuousengagement with each other, the vibratory movements of the inner andouter shell members result in minute components of slippage between theinner and outerl shells, which slippage components materially dampen theshell noise. The present laminated construction is, therefore,substantially free in service of objectionable shell noises.

A further and important advantage has to do with the increased strength'of the silencer as a whole. It will be recognized that the pressureimpulses transmitted through th'e silencer subject the latter tosubstantial forces tending to rupture the shell. In conventionalstructures, the longitudinal lock seam is, of course, a relatively weakpart of the structure, and these forces frequently rupture the lockseam. With the present construction, however, the resistance to ruptureis very materially increased by the provision of the inner shell. Itwill be noticed that the overlap in the inner shell is spaced from thelock seam in the outer shell by approximately The pressure is applied tothe lock seam accordingly not directly, but only through the innershell. The substantial pressures existing within the inner shell act toform a substantial frictional connection between the overlapped edges ofthe inner shell, which frictional engagement enables the inner shell toitself withstand substantial expansive pressures. The inner shell,accordingly, not only functions to reinforce the outer shell, by itselfsustaining a substantial part of the expansive pressure, but alsoprotects the lock seam formed in the outer shell, and prevents theexpansive pressures from being directly applied to the lock seam.

Considerable difficulty has heretofore been experienced in themanufacture of silencers in respect not only to leakage between theseveral silencing or resonating chambers, but also in respect to leakagebetween the interior of the silencer and the outside atmosphere. In theusual manufacture of silencers employing a longitudinal lock seam, ithas been conventional to space the ends of the lock seam a slightdistance inwardly from the ends of the silencer, so as to allow for theformation of the joint between the shell and the heads, which joint isherein illustrated as being a rolled seam. This practice necessarilyintroduces a possibility of leakage between each end of the lock seamand the corresponding rolled or other seam at the end of the shell. Thisdifliculty is entirely overcome with the present arrangement, since, asclearly appears, the inner shellextends entirely to the end of the shellstructure. The pressures acting against the inner shell serve to hold itin tight frictional engagement; with the outer shell, and also serve asmentioned above to produce a substantial frictional engagement betweenthe overlapped edges 16 and 18. Because of the latter frictionalengagement, little, if any, leakage of gases occurs between suchoverlapped edges, and any such.

leakage, in order to escape from the outer shell, would have to travelin the space between the inner and outer shells from the position of theoverlap to the position of the lock seam 12.

In respect to leakage which normally occurs between the silencingchambers positioned within the silencer, it will be appreciated that therolling of the outer shell member tends to introduce some irregularitiesor unevenness in the form thereof, which irregularities afford leakagespaces around the cylindrical partitions such as 24, 26 and 28. In thepresent construction, the inner shell, upon being introduced into theouter shell, expands against the latter, and tends in large part tosmooth out the just mentioned unevenness or irregularities, thusaffording a sub-I stantially true cylindrical surface to receive thepartitions and thereby minimize internal leakage.

The above described laminated construction is further advantageous inthat, as will be appreciated, it lends itself to the provision of asilencer having the non-corrosive inner surface, without at the sametime requiring that the entire shell structure be formed of relativelyexpensive noncorrosive material. That is to say, the outer shell may beformed of relatively inexpensive metal, and the inner shell may beformed of non-corrosive metal, thus affording all the advantages of thenon-corrosive structure, without introducing the expense incident to theuse of noncorrosive metal throughout.

The overlapped relation of the edges of the inner shell is advantageous,not only in respect to the features discussed above, but also in respectto the control of condensation, and the prevention of any condensatefrom entering the space between the inner and outer shells. It is usualto mount the cylinder on the associated vehicle in substantially therotative position shown in Fig. 2, in which the lock seam 12 is at oneside of theA silencer. In the present instance, the overlapped edges 16and 18 are also positioned at the side of the silencer, with the inneredge 18 extending downwardly and inwardly over the compansion edge 16.With this relation, any condensate which accumulates along the innersurface of the shells, and flows downwardly along the side walls, isenabled to ilow across the junction between the edges 16 and 18 withoutentering the space between such edges.

It is believed evident from the foregoing detailed description that thepresent method and arrangement provides an extremely simple andeffective silencer construction, and that various modifications in theform and arrangement of the parts may be made within the spirit andscope of the invention.

What is claimed is:

l. In a silencer for exhaust gases, the combination of a shellstructure, acoustic silencing structure within said shell andcooperating with the shell to define at least one chamber, a portion atleastl of the wall whereof is constituted by said shell, said silencerhaving means for introducing gases into said chamber, said shellcomprising an outer shell-like member and an inner shelllike memberreceived in the outer member, the adjacent surfaces of the members beingin continuous engagement with each other, each said member having alongitudinal joint therein, and said joints being in angularly displacedrelation to each other.

2. In a silencer for exhaust gases, the combination of a shellstructure, acoustic silencing structure within said shell andcooperating with the shell to define at least one chamber, a portionatleast of the wall whereof is constituted by said shell, said silencerhaving means for introducing gases into said chamber, said shellcomprising an outer shell member, and an inner shell member positionedwithin said outer member, said inner member having a longitudinal seamtherein, the adjacent edges of which are freely overlapped on each otherthroughout at least a major portion of the length of said inner shell,and said outer shell having a longitudinal seam therein in angularlydisplaced relation to the rst mentioned seam.

3. In a silencer for exhaust gases, the combination of a shellstructure, acoustic silencing structure within said shell andcooperating with the shell to define at least one chamber, a portion ai,least of the wall whereof is constituted by said shell, said silencerhaving means for introducing gases into said chamber, said shellcomprising an outer shell member, and an inner shell member positionedwithin said outer member, said inner member having a longitudinal seamtherein, said outer shell having a longitudinal seam therein inangularly displaced relation to the first mentioned seam, and a head forenclosing each end of the shell, each head being rigidlly secured toeach shell member, the adjacent edges of said inner shell being freelyoverlapped on each other except in the regions where said inner shell issecured to said heads.

CHESTER C. MOSS.

